Yol. 55-] AGGLOMEEATES AND TUFFS OF CONGLETON EDGE. 549 



occurring at Tissington towards the close of the deposition of the 

 Carboniferous Limestone. The object of the present paper is to 

 bring forward distinct evidence, hitherto unsuspected, of volcanic 

 action of the same age on the western slopes of Congleton Edge, 

 20 miles west of Tissington. 



This bed of igneous rock, though well exposed in an old quarry, 

 seems hitherto to have escaped notice. It is omitted from the 

 section in the Geological Survey memoir^ and not mentioned in the 

 text. The late Dr. Garner may possibly refer to it in his ' Natural 

 History of the County of Stafford,' 1844, p. 212, where he says : — 

 ' On the western side of the coalfield, towards Mow Cop, there like- 

 wise occurs a rock which appears to owe its formation in part to 

 igneous action. This is of a lively green colour, very hard, and 

 enclosing many roundish pieces of bright red rock, which, however, 

 are also seen in some of the grit of this spot.' But this description 

 scarcely agrees with the coarse angular nature of the agglomerate at 

 present exposed in the quarry at the foot of Congleton Edge. 

 Again, in the appendix to the same work, p. 45, he says : — ' The 

 Astbury limestone at the west foot of Mow Cop is rather peculiar, 

 being dark in colour, with blotches of red and green.' This may 

 refer to some of the included fragments of tuff, or to the pockets 

 of haematite and other minerals which occur in the heart of the 

 limestone. 



2. General Structure of the Area. 



The area under discussion lies in the Geological Survey map, 

 Sheet 81 S.W. 



The ridge of Mow Cop, with its northern extension, Congleton 

 Edge, forms the boundary between Staffordshire and Cheshire, and 

 reaches an elevation of 1101 feet above Ordnance datum on Congle- 

 ton Cloud. The ridge, whose scarp faces west, is capped by two 

 beds of Millstone Grit, considered to represent the First and Third 

 Grits, separated by a small amount of black shales. Below the Third 

 Grit to the base of the hill a narrow dome of Carboniferous Limestone, 

 lying in the midst of the so-called Yoredale Shales, is exposed in an 

 old quarry. Immediately to the west, the Lower Carboniferous rocks 

 end off against the Red Hock Eault, while the whole country is 

 covered with a thick mantle of Glacial clays and sands. In order to 

 bring out clearly the exact age and relationship of these igneous 

 rocks to those of known age, a small tract — a little under one square 

 mile — has been carefully examined and mapped on the 25-inch 

 scale, and a reduction of this map is reproduced in fig. 1. The 

 authors were so fortunate as to obtain, in the quarry-section of 

 agglomerate, the help of Mr. Arnold-Bemrose, who also kindly 

 furnishes some notes on the petrography of the igneous rocks. 



' 'Geol. of Country round Stockport, Macclesfield, Congleton, & Leek,' 

 Mem. Geol. Surv. 1866, pp. 9, 47, 72 & 73. 



